The man and woman appear oblivious of the chaos swirling around them. When anarchy erupted on the streets of Vancouver last week, the couple exchanged an ephemeral kiss that will last forever on our cultural landscape. Photographer Richard Lam inadvertently captured the embrace on his camera, and the image quickly made headlines around the world. It’s a striking contrast of furious energy and tender pause that will be analyzed, criticized, and admired for decades to come. Scott Jones and Alex Thomas were the calm in the eye of a storm.

Many wonder whether the scene has been photo-shopped or staged. Who are these people and what would inspire such seemingly inappropriate behaviour under dire circumstances? Yet a glimpse at some of the science behind why we kiss suggests that the lip lock was, in reality, a very natural response to being involved in an unfamiliar, frightening situation as emotions ran high.

There’s no doubt that being caught up in a riot would lead to increased levels of adrenalin, which boosts our heart rate and makes us sweat. Adrenalin causes our blood vessels to dilate, quickens the pulse, flushes our cheeks, and can even make breathing irregular. This important chemical is involved in readying our bodies to anticipate what might occur next. A passionate kiss can cause the same response because it also boosts adrenalin. And during an extremely tense situation, it’s easy to understand why sensations can be confused, blurring perceptions of passion and anxiety.

In the flurry of interviews that followed the photograph’s publication, Jones told reporters that he kissed his girlfriend in order to calm her down after police knocked them to the ground. Surely this was a split-second decision, but the odds are good that this strategy worked thanks to the cocktail of chemicals coursing through our bodies that regulate the way we feel and behave.

A kiss can be soothing for myriad reasons, and has been documented to reduce levels of the “stress hormone” known as cortisol. When we experience stress, cortisol is responsible for raising blood sugar and blood pressure while suppressing the immune system. It is part of the body’s regulatory system that amps us up to perform well under pressure. The right kiss from someone we love lowers levels of this hormone, thereby reducing the uneasiness we feel. In other words, whether he was consciously aware of it or not, Jones’s kiss likely served its intended purpose.

Of course, cortisol and adrenalin do not act alone. They are just two soldiers in an army of chemicals that guide our actions. Kissing also raises levels of the “love hormone” oxyto-cin, which reaffirms the special bond we share with those who matter most to us. And it is not all about romance either. When parents intuitively press their lips to a child’s scraped knee and say “all better,” it can actually decrease the perception of pain and discomfort.

Our brains are also primed to associate kissing with feelings of love and security. A newborn’s earliest feeding experiences involve similar movements and mouth pressure, laying down the neural pathways in his brain that will be continue to be important in other relationships throughout his life. On top of that, our lips are packed with sensitive nerve endings, so even the slightest brush sends a cascade of information to our brains that often feels very good.

It should be no surprise that kissing acts like a drug by stimulating the natural chemicals in our bodies because it has inspired poets, musicians, and lovers over millennia. And no matter what particular mix of neurotransmitters, hormones -and perhaps, bit of magic -led to that moment in Vancouver, it serves as an indelible reminder of the single most universal and humanizing practice we all share: The kiss.